Apparatus for filling and, if desired, emptying inert gas poor in oxygen into or from holds in ships, respectively

ABSTRACT

Exhaust gases from an emergency or auxilliary gas turbine/generator set are passed to an afterburner in which the rather high oxygen content of said exhaust gases is reduced to an acceptable level for use of the resulting gas as an inert explosion-proof gas for empty oil tanks. Before the gas is supplied to the tanks it is cooled by water supplied by a pump driven by the electric current produced by the generator. No blowers are required, since the turbine may operate against the pressure required for feeding the gas through the afterburner and the cooler and into the tanks. For displacing the inert gas from the tanks when desired, compressed air from the compressor unit of the turbine/generator set is tapped off and passed through an injector in which additional air from the atmosphere is entrained. The combined air is passed through the cooler and fed to the tanks through a suitable distribution system.

United States Patent 3 1 Westrum Dec; 4, 1973 [75] Inventor: ThorbjiirnWestrum, Kongsberg,

Norway [73] Assignee: A/S Kongsberg Vapenfabrikk,

- Konsberg, Norway 22 Filed: Oct. 1, 1971 21 App1.No.: 185,597

[30] Foreign Application Priority Data 1/1939 Willenborg 23/281 PrimaryExaminer-George E. A. l-lalvosa Assistant Examiner- -Stuart M. GoldsteinAttorney-l-lolman & Stern [57] ABSTRACT Exhaust gases from an emergencyor auxilliary gas turbine/generator set are passed .to an afterburner inwhich the rather high oxygen content of said exhaust gases is reduced toanacceptable level for use of the resulting gas as an inertexplosion-proof gas for empty oil tanks. Before the gas is supplied tothe tanks it is cooled by water supplied by a pump driven by theelectric current produced by the generator. No blowers are required,since the turbine may operate against the pressure required for feedingthe gas through the afterbumer and the cooler and into the tanks. Fordisplacing the inert gas from the tanks when desired, compressed airfrom the compressor unit of the turbine/generator set is tapped off andpassed through an injectorin which additional air from the atmosphere isentrained. The combined air is passed through the cooler and fed to thetanks througha suitable distribution system.

4 Claims, 1 Drawing Figure BACKGROUND OF THE INVENTION I The presentinvention relates to a method and an apparatus for filling and, ifdesired, emptying inert gas,

poor in oxygen, into or from holds or rooms in ships, respectively, inwhich method and apparatus combustion gases are produced in a combustiondevice, which gases are cooled and supplied to the holds to be filled.

A number of serious explosion accidents in tankers have proved that itis important to control the gas content of ships tanks so that the gasmixture is explosionproof. Plants or apparatus have therefore beendeveloped, in which the exhaust gases from the burners serving for theproduction of steam for the main engine and/or auxilliary engines of theship are supplied to the tanks of the ship as the tanks are emptied ofoil. Such an apparatus has the advantage that the costs thereof aremoderate, and that it has a relatively low power demand (for theoperation of a blower supplying the exhaust gases to the tanks, with thedesired overpressure). However, such apparatus also have several.disadvantages. Firstly, the oxygen content of the exhaust gases variesconsiderably. The apparatus further depends upon the steam boilers beingin operation and upon. theoperating condition of the boilers. Theexhaust gases entrain impurities and cause deposits on the blowers,valves and conduits. Sulphuric or sulphurousacid may be present in theexhaust gases, and the required The apparatus of the invention isprimarily characterized in that it is adapted to be connected to theexhaust conduit from a gas turbine which also serves other purposes, forinstance the operation of a generator, said apparatus comprisinganafterburner for reduction of the oxygen content of theexhaust gases,'a cooler for reduction of the temperature of the gases, a dischargeconduit for the cooled combustion gases and a valve for controlling thesupply of exhaust gases to maintain the pressure of the inert gas withinthe desired limits.

Gas turbines are often installed as an auxilliary or emergency setonboard ships. Such sets are mostly not in use when the ship isunloading, and the set is then available for the production of inert gasfor the filling of the oil tanks of the ship as these tanks are emptied.It is true that the exhaust gases from a gas turbine are not directlysuited as an inert gas for said purpose, since the oxygen content iscomparatively high. However,

the oxygen content is relatively constant, and the ex- .haustgasestherefore lend themselves to an afterburninto tanks and other holdsor rooms in the ship. Such blower is seriously exposed to corrosion;Therefore, the I apparatus requires a rather large amount ofmaintenance. In addition, the blower requiredfor blowing the exhaustgases into the tanks of the ship produce rather much noise. Further, thesystem depends upon the presence of aburner for a steam boiler.

There have alsobeen developed plantsorapparatus working with separategas generators, i.e; burners especially adapted for the production of aninert g'as,.poor in oxygen, for use in ships tanks. Suchapparatusproduce a very pure gas with low. oxygen and sulphur-com tentsand is, of course, independentof-afiring-of steamboilers. Thedisadvantages of such an apparatus are.

that it is extremely expensive and has a very. large.

power demand and fuel consumption.

SUMMARY OF THE INVENTION The object of the presentinvention is toprovide a method and an apparatus 'of the kind iinitially referred to,which does neither depend on steam boiler bumersnorrequire any blowerfor providing the. required pressure of the inert gases, but is stillsubstantially cheaper 5Q thepressure is reduced and additional air isdrawn in.

than an apparatus having a separate gas generator. The

inertgas is primarily intended for the filling of empty oil tanks, butmay also be used for instance in extin-p guishing fire in engine rooms.I

Themethod of the invention is characterized in that asa combustiondevice there is used .agas turbine .holds by the pressure downstream of.the turbine-and! without the aid of blowers.

a back-pressure downstream of the turbine will of course reduce theoutput of the turbine. However, the remaining output will be sufficientnot only for operating a cooling water pump for cooling theexhaustgases,

but also for supplying electric current to the electric distributionnetwork of the ship during the unloading period. As an example, it maybe mentioned that a gas inert gas apparatuswitha gas turbine isthat'thereby a simple possibility is provided for removing the inert gasfrom the holds of the shipwhen this is required. Thus, according to theinvention, air having the required pressure for displacing the inert gasfrom the holdsof the ship may, be supplied from the compressor unit of ithe gas turbine; a portion of the air compressed in the compressor beingpassed through an injector in which Air of suitable pressure suppliedfrom the injector is passed through the cooler of the apparatus toreduce the temperature of theair and further to the tanks in order todisplace the inert gas therein. In the apparatus of the inventionthis-possibility is provided for by the fact that the apparatuscomprises an airconduit for connection to the pressure side of thecompressor unit of the turbine and delivery of compressed air to thedischarge conduit through the coolerand an injector inserted in said airconduit and operated by the com pressed air from the compressor to drawadditional air into the airconduit. 7

Further features of the invention will appear from the followingdescription of an embodiment, reference being had to the accompanyingdrawing, which illus-. trates the operating principles of an apparatusaccord ing to the invention.

DETAILED DESCRIPTION OF THEIDRAWING [n the drawing, the elementsincluded in a conventional auxilliary and/or emergency set driven by agas turbine are indicated within a frame G shown by a dotand-dash-line.These elements consist of the gasturbine itself, which in the drawinghas been divided into its three functional units, viz. a compressor 1, acombustion chamber 2 and a turbine 3. The generator is indicated at 4,whereas 5 is an oil tank for operation'of the gas turbine, the oil beingsupplied to the combustion chamber 2 of the gas turbine set by a pump 6.The exhaust gases from the gas turbine are ordinarily let out into theatmosphere through an exhaust conduit 7 and an exhaust pipe 8 within theships funnel.

The inert gas apparatus according to the invention is based upon thepresence of such a gas turbine set and is connected to this set in thefollowing way:

An exhaust conduit 9 is connected to the exhaust conduit 7. Thedistribution of the exhaust gases on the exhaust pipe 8 and the exhaustconduit 9 is controlled by a throttle valve 10 in the exhaust pipe 8 ina manner which will be described later in more detail. When the inertgas apparatus is not in operation, the exhaust conduit 9 is closed by avalve 11. I

The exhaust gases from the exhaust conduit 9 are passed to anafterburner 12 having a fuel nozzle 13 fed from the fuel tank 5 througha conduit 14 by means of a pump 15. The fuel amount is controlled in amanner which will be described later in more detail.

The afterburner is required primarily to reduce the oxygen content ofthe exhaust gases from the gas turbine. Typically, such exhaust gasesfrom the gas turbine may have the following analysis:

percent by volume:

Downstream of the afterburner the exhaust gases may have the followingcomposition:

percent'by volume:

0 about 1 I The exhaust gases from the afterburner 12 are passed into acooling tower 16 in which they are cooled by spraying with sea watersupplied through a conduit 17 by means of a cooling water pump 18. Thecooling water collects in the bottom of the cooler 16 and is dischargedinto the sea through a conduit 19.

The cooled gases are passed through a water separator 20 and furtherthrough a discharge conduit 21 leading to a distributing system notshown.

charge conduit 21 is excessive, the flow of fuel through the valve 25 isfurther throttled, whereby more fuel will be supplied to the afterburner12 through the fuel nozzle 13. If the oxygen content in the exhaustgases. lies below a certain limit, this must be taken as an indicationthat an incomplete combustion may take place in the afterburner l2, andthat the exhaust gases may contain an excessive amount of carbonmonoxide. The flow through the valve 25 will then be increased so thatthe fuel supply to the fuel nozzle 13 is reduced.

The oxygen analyser 24 also actuate s a valve 27 in the dischargeconduit 21 and a valve 28 in a conduit 29 branched from the dischargeconduit 21 and leading to the atmosphere. The valves 27 and 28 are socontrolled that the exhaust gases are passed to the ships holds throughthe distribution system not shown, only when the oxygen content lieswithin predetermined limits, whereas the gases are passed to theatmosphere through the conduit 21 when the oxygen content is too high ortoo low, a low oxygen content being, as already mentioned, interpretedas an indication of an excessive carbonmonoxide content. 34 is a safetyvalve.

When the apparatus according to the invention is to be used fordisplacing the inert gas from the holds in the ship by means of freshair having the required pressure, the valve 1 1 will be closed and theafterburner 12 and the described control devices will be out ofoperation. A portion of the air compressed by the compressor 1 isdiverted through a conduit 30. This, of course, reduces the output ofthegas turbine 3, and it must be expected that the generator 4 cannot besubjected to a load during this period-The compressed air from theconduit 30 is supplied to an injector 31 which reduces the pressure ofthe air and at the same time draws in additional air through an airinlet 32. From a gas turbine' set of the capacity previously referred toit is possible to tap ofi' about 9,000 standard m air per hour at apressure of approximately 37 psia. A corresponding amount of air may bedrawn into the injector so that in the conduit 33 from the injector 31there may flow about 18,000 standard m ,air per hour having a pressureof about 18.5 psia. The temperature of the air tappedfrom the compressoris about 170 C; This temperature is reduced in the injector partlybecause of the expansion and partly because of admixture with air drawnin through the air inlet 32. The air in the conduit 33 will thereforehave a temperature of about C. For further cooling this air is passedinto the cooler 16 and further through the discharge conduit 21 into thedistribution system (not shown) for fresh air.

A gas turbine set of the capacity previously referred to will produceabout 31,000 standard m exhaust gas per hour, and when the pressure inthe exhaust conduit downstream of the turbine is to be 18.5 'psia, thetemperature of the exhaust gases will be about 550 C. The exhausttemperature will of course rise further in the after-burner, and whenthe apparatus is to supply inert gas, comparatively large amounts ofcooling water (about 1,500 m per hour) will be required in the cooler12. As previously indicated the pump 18 for circulating this amount ofcooling water may be operated with an input of about 300 kW, which maybe provided by the gas turbine set. When the set supplies air fordisplacing the inert gas from the tanks, a substantially lower amount ofcooling water is required, since in this case only about 18,000 standardm air per hour must be cooled from a temperature of about 100 C.

What I claim is 1. Apparatus for filling and, if desired, emptying inertgas, poor in oxygen, into or from holds in ships, respectively, saidapparatus being connected to the exhaust conduit from a gas turbine,said apparatus comprising an afterburner for reduction of the oxygencontent of the exhaust gases of the turbine, a cooler for reduction ofthe temperature of the gases, at discharge conduit for the cooledcombustion gases and a valve for controlling the supply of exhaust gasesto maintain the pressure of the inert gas within the desired limits.

2. Apparatus as claimed in claim 1, characterized by an oxygen analyserfor analysing the oxygen content of the supplied inert gas and a valvefor controlling the supply of fuel to the afterburner said valve beingcontrolled in accordance with the result of the analysis.

3. Apparatus as claimed in claim 2', characterized by a branch conduitleading from the discharge conduit for inert gas into the atmosphere andone or more valves controlled by the oxygen analyser for supplying gasto the branch conduit instead of the discharge conduit when the oxygencontent is not within the prescribed limits.

4. Apparatus as claimed in claim 3, characterized by an airwconduit forconnection to the pressure side of the compressor unit of the turbineand delivery of compressed air to the discharge conduit through thecooler and an injector inserted in 'said air conduit and operated by thecompressed air from the compressor to draw additional air into the airconduit.

1. Apparatus for filling and, if desired, emptying inert gas, poor inoxygen, into or from holds in ships, respectively, said apparatus beingconnected to the exhaust conduit from a gas turbine, said apparatuscomprising an afterburner for reduction of the oxygen content of theexhaust gases of the turbine, a cooler for reduction of the temperatureof the gases, a discharge conduit for the cooled combustion gases and avalve for controlling the supply of exhaust gases to maintain thepressure of the inert gas within the desired limits.
 2. Apparatus asclaimed in claim 1, characterized by an oxygen analyser for analysingthe oxygen content of the supplied inert gas and a valve for controllingthe supply of fuel to the afterburner said valve being controlled inaccordance with the result of the analysis.
 3. ApparatuS as claimed inclaim 2, characterized by a branch conduit leading from the dischargeconduit for inert gas into the atmosphere and one or more valvescontrolled by the oxygen analyser for supplying gas to the branchconduit instead of the discharge conduit when the oxygen content is notwithin the prescribed limits.
 4. Apparatus as claimed in claim 3,characterized by an air conduit for connection to the pressure side ofthe compressor unit of the turbine and delivery of compressed air to thedischarge conduit through the cooler and an injector inserted in saidair conduit and operated by the compressed air from the compressor todraw additional air into the air conduit.